[dpdk-dev] [PATCH] lib: move rte_ring read barrier to correct location

[Juhamatti Kuusisaari <juhamatti.kuusisaari@coriant.com>]

Fix the location of the rte_ring data dependency read barrier.
It needs to be called before accessing indexed data to ensure
that the data itself is guaranteed to be correctly updated.

See more details at kernel/Documentation/memory-barriers.txt
section 'Data dependency barriers'.

Signed-off-by: Juhamatti Kuusisaari <juhamatti.kuusisaari@coriant.com>
---
 lib/librte_ring/rte_ring.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index eb45e41..a923e49 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -662,9 +662,10 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void **obj_table,
                                              cons_next);
        } while (unlikely(success == 0));

+       rte_smp_rmb();
+
        /* copy in table */
        DEQUEUE_PTRS();
-       rte_smp_rmb();

        /*
         * If there are other dequeues in progress that preceded us,
@@ -746,9 +747,10 @@ __rte_ring_sc_do_dequeue(struct rte_ring *r, void **obj_table,
        cons_next = cons_head + n;
        r->cons.head = cons_next;

+       rte_smp_rmb();
+
        /* copy in table */
        DEQUEUE_PTRS();
-       rte_smp_rmb();

        __RING_STAT_ADD(r, deq_success, n);
        r->cons.tail = cons_next;
--
2.9.0


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